get_biomart: Get Ensembl biomaRt object
In jgockley62/UW_RNASeq: Identify differentially expressed genes counts data

Get GC content, gene Ids, gene symbols, gene biotypes, gene lengths and other metadata from Ensembl BioMart. Object returned contains gene Ids as rownames.

1	get_biomart(count_df, gene_id, synid, version, host, filters, organism)

`count_df`	A counts data frame with sample identifiers as rownames.
`gene_id`	Column name of gene Ids
`synid`	A character vector with a Synapse Id.
`version`	Optional. A numeric vector with the Synapse file version number.
`host`	An optional character vector specifying the release version. This specification is highly recommended for a reproducible workflow. (see `"biomaRt::listEnsemblArchives()"`)
`filters`	A character vector listing biomaRt query filters. (For a list of filters see `"biomaRt::listFilters()"`)
`organism`	A character vector of the organism name. This argument takes partial strings. For example,"hsa" will match "hsapiens_gene_ensembl".